The branch concentrations (ratios of branches) of polyolefin, including polyethylene and the like, are regarded as the main factor that affects the properties of products including melting, crystallinity, etc. Conventional methods of analyzing the branch concentrations are problematic because the testing time is long, whereby the type of sample that can be tested is limited and the feedback of analysis results is inevitably late. Hence, analysis methods are required to be improved in terms of shortening the testing time and increasing the sample preparation efficiency.
Conventionally useful in analyzing the branch concentrations of polyolefin, carbon NMR (Nuclear Magnetic Resonance) undesirably requires a measurement time of about 12 hr or longer. For example, there are provided analysis methods including measurement of the branch concentrations and qualitative and quantitative analysis of comonomers through 13C-NMR, mentioned in a paper by Professor Randall (Carbon-13 NMR of ethylene-1-olefin copolymers: Extension to the short-chain branch distribution in a low-density polyethylene, Journal of Polymer Science: Polymer Physics Edition Volume 11, pages 275-287, February 1973). However, such methods are disadvantageous because of the long testing time and doubtful accuracy of values upon measuring short-chain branching using calibration curves, such as NIR, GPC, etc. In this regard, Korean Patent Application Publication No. 2007-0088724 discloses a method of analyzing the structure of a compound using H-NMR and 13C-NMR, but methods of analyzing the ratios of polyolefin branches have not yet been introduced.
Accordingly, there is a need for novel analysis methods that are able to drastically reduce the measurement time and are also able to analyze low-concentration samples.